1. Field of the Invention
The present invention relates to an apparatus and a method for fabricating liquid crystal display (LCD) panels. More particularly, the present invention relates to an apparatus and a method for efficiently examining seal patterns used in attaching substrate together.
2. Discussion of the Related Art
Generally, LCD devices display images by applying data signals to an array of pixels to thereby control light transmittance characteristics of the pixels, wherein the data signals are derived from external image information. A typical LCD device includes a unit LCD panel having a plurality of pixels arranged in a matrix pattern, and gate and data driving units for driving the pixels.
The LCD panel typically includes a color filter substrate attached to a thin film transistor (TFT) array substrate by a seal pattern formed at a peripheral region of an image display area. The attached color filter and TFT array substrates are separated from each other to define a cell-gap that contains a liquid crystal layer.
The color filter substrate supports a common electrode while the TFT array substrate supports a plurality of gate lines, a plurality of data lines crossing the plurality of gate lines to define a plurality of pixels, a plurality of TFTs arranged at crossings of each of the gate and data lines, and a plurality of pixel electrodes electrically connected to corresponding ones of the TFTs. Alignment films, formed on opposing surfaces of the TFT array and color filter substrates, are rubbed to induce a predetermined orientation of molecules within the liquid crystal layer.
The data lines transmit data signals, supplied from the data driving unit, to the pixels while the gate lines transmit scan signals, supplied from the gate driving unit, to the pixels. In response to scan signals, sequentially supplied from the gate driver, the TFTs switch data signals transmitted by the data lines to corresponding pixel electrodes.
When data and reference signals are applied to the pixel and common electrodes, respectively, an electric field is generated within the liquid crystal layer. Due to anisotropic dielectric properties of molecules within the liquid crystal layer, the generated electric field rotates liquid crystal molecules between the common electrodes and the pixel electrodes. When the liquid crystal molecules rotate, the light transmittance characteristics of the pixels change. Thus, by controlling the magnitude of the generated electric field via the data and reference signals, light transmittance characteristics of the plurality of pixels may be controlled to display an image.
FIG. 1 illustrates a plan view of a related art LCD panel.
Referring to FIG. 1, the related art LCD panel 100 includes an image display area 113 having a plurality of pixels are arranged in a matrix pattern, a gate pad area 114 containing a plurality of gate pads that are connected to gate lines in the image display area 113, and a data pad area 115 containing a plurality of data pads that are connected to data lines in the image display area 113.
The image display area 113 generally includes the portion of a TFT array substrate 101 that is overlapped by a color filter substrate 102. Accordingly, the image display area 113 typically includes the portion of the TFT array substrate 101 that supports a plurality of gate and data lines crossing each other to define pixels, pixel electrodes formed within the pixels, and TFTs arranged at crossings of the gate and data lines and connected to corresponding pixel electrodes for driving the pixel electrodes. A protecting film (not shown) is formed over the entire surface of the TFT array substrate 101 to protect the pixel electrodes and the TFTs. Further, the image display area 113 typically includes the portion of the color filter substrate 102 that supports a black matrix, a plurality of color filters separated by the black matrix, and a common transparent electrode opposing the pixel electrodes.
The gate pad and data pad areas 114 and 115 are found at edges of the TFT array substrate 101 that are not overlapped by the color filter substrate 102. Accordingly, the gate pad area 114 includes a plurality of gate pads that transmit scan signals, supplied by a gate driving unit (not shown), to corresponding ones of the gate lines. Similarly, the data pad area 115 includes a plurality of data pads that transmit image information, supplied by a data driving unit (not shown), to corresponding ones of the data lines.
The TFT array substrate 101 and the color filter substrate 102 are joined to, and spaced apart from, each other via a seal pattern 116 formed at the periphery of the image display area 113 to define a cell-gap. Uniformity of the cell gap is maintained by a spacer structure (not shown) and a liquid crystal layer is formed within the cell gap.
Recently, a process has been developed that facilitates the simultaneous fabrication of a plurality of the LCD panels (such as those shown in FIG. 1), thereby increasing the production yield of such LCD panels. Typically, a plurality of TFT array substrates 101 are formed on a first base substrate, larger than each individual TFT array substrate 101; a plurality of color filter substrates 102 are formed on a second base substrate, larger than each individual color filter substrate 102; the first and second base substrates are joined to each other via the seal pattern 116; and the joined first and second base substrates are then cut and processed to form individual (i.e., unit) LCD panels 100.
A liquid crystal injection hole is often formed in the seal pattern 116 and, after the joined first and second base substrates are cut, liquid crystal material can be injected through the liquid crystal injection hole and into the cell-gap of each unit LCD panel 100 to form the liquid crystal layer. Subsequently, the liquid crystal injection hole is sealed to prevent leakage of the injected liquid crystal material outside the image display area 113.
To ensure the reliability of each LCD panel 100, the seal pattern 116 must be examined to determine the presence of any defective breaks in the seal pattern 116 (i.e., breaks in the seal pattern 116 not including the liquid crystal injection hole). Generally, such examination is performed with an operator's naked eye wherein the operator stops the LCD panel production line after forming seal patterns 116 on a predetermined number of substrates (e.g., three or four), opens the seal pattern forming equipment, illuminates a seal pattern 116 with a lamp, and examines the seal pattern 116.
During the examination process described above, foreign material can be introduced onto the substrate when the seal pattern forming equipment is opened and/or when the operator actually examines the seal pattern 116. When introduced onto either the TFT array or color filter substrates 101 or 102, the foreign material creates a defective LCD panel 100. Moreover, because the examination process is performed only periodically, there is an increased likelihood that seal patterns 116 with defective breaks (e.g., breaks in portions of the seal pattern 116 other than the liquid crystal injection hole), will pass through the seal pattern forming equipment undetected, increasing the risk of forming an LCD panel 100 with a defective seal pattern 116. If liquid crystal material is subsequently injected into LCD panels having defective seal patterns 116, liquid crystal material may leak from the image display area 113 and/or the defective breaks in the seal pattern 116 must be sealed. As a consequence, material expenses incurred during LCD panel fabrication increase. Lastly, because an operator must stop the LCD panel production line to opens the seal pattern forming equipment to examine the seal pattern 116, and then restart the LCD panel production line to resume fabrication of the LCD panels, the related art examination process reduces the efficiency with which LCD panels 100 are fabricated.